1. Field
This disclosure relates to a positive active material for a rechargeable lithium battery and a rechargeable lithium battery including the same are disclosed.
2. Description of the Related Technology
Rechargeable lithium batteries have recently drawn attention as a power source for small portable electronic devices. They use an organic electrolyte and thereby have twice or more discharge voltage than that of a conventional battery using an alkali aqueous solution, and accordingly have high energy density.
As for a positive active material for a lithium rechargeable battery, a lithium-transition metal oxides being capable of intercalating lithium, such as LiCoO2, LiMn2O4, LiNi1-xCoxO2 (0<x<1), and the like, have been investigated.
As for a negative active material for a lithium rechargeable battery, various carbon-based materials such as artificial graphite, natural graphite, and hard carbon capable of intercalating and deintercalating lithium ions have been used. Since graphite, among the carbon-based materials, has a low discharge potential relative to lithium of about −0.2V, a battery using graphite as a negative active material has a high discharge potential of about 3.6V and excellent energy density. Furthermore, the graphite guarantees a long cycle life for a battery due to its outstanding reversibility hence it is widely used as a negative active material.
However, a graphite active material has a low density (theoretical density: about 2.2 g/cc) and consequently a low capacity in terms of energy density per unit volume in an electrode. Further, a battery may swell and thus, because graphite may side react with an organic electrolyte at a high discharge voltage have decreased capacity.
Alternative materials have been investigated in order to solve these problems in using graphite as a negative active material. For example, an oxide negative active material such as tin oxide, lithium vanadium-based oxide, and the like has recently been investigated. However, the oxide negative active material does not realize sufficient cell performance and thus, additional research is needed.